The present invention relates to a device for delivering a self-expanding stent into a vessel of the body, with a tubular sheath which, in a distal section, keeps the stent radially compressed, a pusher element which is guided in the tubular sheath, in order to stabilize the stent when the sheath is pulled back, and a handle that has a passage via which the pusher element is secured on the grip.
Insertion systems of this kind and stents are generally known from the prior art.
Such insertion systems are used to implant endovascular stents into blood vessels that have been damaged, for example as a result of diseases or the like, or that have been widened by an aneurysm or have had their lumen occluded, as a consequence of which the function of the vessels is greatly impaired or there is a risk of the vessels rupturing. In the prior art, various implantable stent devices are known which, after they have been implanted, keep blood vessels, for example arteries, open or delimit aneurysms from the blood stream. Such stents generally have a tubular body which is inserted into the vessel and is fixed at the relevant location in order to keep the lumen of the vessel open.
Thus, the prior art includes stent grafts, for example, which have a wire framework made of a self-expanding material, and the wire framework can additionally be connected with a tube made of textile or PTFE.
For implantation, the stent or stent graft is radially compressed, such that its cross-sectional surface area can be considerably reduced and it can easily be inserted into the vessel. On account of the resiliency of the metal framework or metal stent, the stent expands back to its original shape and in so doing stretches its jacket surface, which wedges itself internally in the blood vessel.
For implantation, the stents are folded up radially and, with the aid of catheters advanced through the lumen, are then introduced into the blood vessel and placed in the correct position in the vessel. The correct position of the stent can be monitored using X-ray markers, for example. To ensure that the stents remain in the folded-up state during their positioning, they are arranged in a sheath or in a sheath-like tube, which presses the stent radially inwards and compresses it. This so-called withdrawal sheath is pulled back after the stent has been positioned in the vessel, in which process the stent is held axially by an abutment element/slide element, which is also designated as a pusher. The pusher lies in contact with the stent and holds the latter in its axial position, while the withdrawal sheath also surrounding the pusher is detached from the stent, which is thus able to expand and wedge itself in the blood vessel.
When releasing a self-expanding stent or stent graft, the physician often has to apply a considerable force to the pulling grip of the tubular sheath and to the grip used for positioning the implant and connected to the pusher.
The force applied is necessitated, on the one hand, by friction between the outer wall of the stent/stent graft, strongly compressed counter to its expansion forces, and the inner wall of the tubular sheath, and, on the other hand, also by frictional forces between the movable parts of the insertion system and deflecting force components caused by anatomical windings of the access vessel and aorta.
Moreover, the operating physician has to bear in mind that, when removing the sleeve, the stent ought not to be able to shift from the location at which it is specifically intended to be placed.
The considerable force applied when releasing an aortic stent graft places a physical strain on the physician and can lead to an abrupt release of the stent/stent graft on transition from static friction to kinetic friction in the insertion system. In this situation, it is very difficult for the physician to compensate the abrupt release movements on the insertion system such that he can precisely maintain the position of the stent graft with the pusher and at the same time avoid a slipping movement and resulting damage to the vessel wall.
EP 1 117 341 A discloses a delivery system for implantable stents, said system comprising a stabilizing element with a tubular spring, which extends through the catheter between the outer jacket and the inner tube in order to maintain the position of the stent when the outer jacket (pusher) is pulled back. The system disclosed in EP 1 117 341 A also comprises a grip which is designed as an elongate housing with a passage, and a movable element which is guided in the housing and has a pawl hub, one side of which is in engagement with a stationary ratchet, and the other side of which is in engagement with a movable ratchet. The movable ratchet is in engagement with a pinion, and the latter is in turn in engagement with a drive wheel, which is located on the housing. All the elements—stationary ratchet, movable ratchet and movable element—are guided in the housing. The device is actuated manually via a lever provided on the grip.
The prior art also includes delivery systems with what are known as pistol grips, but these are not very ergonomic, and the awkward operation of the system during release of the stent graft can lead to a clenched hold on the part of the user.